The present invention relates to a method of making a pn-junction in a silicon substrate and, more particularly, to positional stabilization of etching mask boundaries in anisotropic etching of structures in a silicon substrate.
A method of making a pn-junction in a silicon substrate is known, including making a silicon layer on a monocrystalline silicon substrate and doping the silicon layer oppositely from the silicon substrate so that the silicon layer is of a doping type which is opposite to the silicon substrate.
Such methods for doping silicon are described in "Mikromechanik" by A. Heuberger, in Section 3.1.2, pp. 91 to 97, Springer Verlag, 1989. One possibility for doping includes diffusion from the gas phase or doped surface coatings. Another possibility is that the doping atoms can be added to the substrate by an externally produced and accelerated ion beam. Additional engineering methods for layer deposition are described in the above cited reference in Section 3.1.5, pp. 114 to 121, e.g. epitaxial layer formation of layers with predetermined doping profiles.